The principle of vaccination is based on two key elements of adaptive immunity, namely specificity and memory. Memory cells allow the immune system to mount a much stronger response on the second encounter with antigens. This secondary response is both faster to appear and more effective than the primary response. The aim in vaccine development is to alter a pathogen or its toxin in such a way that they become innocuous without losing antigenicity. This is possible because antibodies and T cells recognize particular parts of antigens, the epitopes, and not the whole organism or toxin. For example, a toxin produced from a bacterium may be modified, e.g. by formalin treatment, so that it retains its epitopes but loses its toxicity. The resulting toxoid is used as a vaccine. Viruses may be attenuated and/or inactivated so that they retain their antigenicity but lose their pathogenicity.
Neonatal calf diarrhea, also known as calf scours and calf enteritis, is a serious, contagious disease caused by a variety of organisms, including Escherichia coli, Clostridium. perfringens, rotavirus and coronavirus, often in combination and/or with other bacteria, viruses and intestinal parasites. Although antibiotics given to scouring calves can help control bacteria, over-relying on them is ineffective, as they are ineffective against viral or parasitic infections. Moreover, antibiotics reduce the number of beneficial bacteria in the gut, and use over extended periods can lead to microorganisms becoming resistant to antimicrobial drugs used for treatment, e.g. antibiotic resistant bacteria—particularly E. coli. 
For many years, extensive research has been directed toward the preparation of safe and effective veterinary scours vaccines. A number of scours vaccines are currently marketed for use in cattle and other animals. These vaccines are generally classified as attenuated or inactivated, referring to the final vaccine product containing a modified live virus or a killed virus. The scours veterinary vaccines currently marketed include, e.g., ScourGuard™, and are known to be of limited efficacy.
Calf scours, the leading cause of economic loss and death in calves, is usually caused by a combination of factors. Hence, a vaccine to prevent scours should include protection against the four most common causes of scours: coronavirus, rotavirus, E. coli and Cl. perfringens Type C. Attaining high levels of antibody in the colostrum through the use of potent vaccines has proven extremely effective in preventing calf scours. The most effective vaccination program is one in which the level of antibodies in the dams' system peaks at or just prior to calving, providing maximum protection to the calf via the colostrum. Historically, immunization required vaccines to be given within two weeks to a month pre-calving, and required two and sometimes three doses. Vaccination of cows close to calving is a management problem that can overly stress both the cow and the fetus. The vaccines of this invention provide maximum protection while minimizing such stress.
Bovine coronavirus (BCV) causes both enterocolitis and respiratory tract infections in calves and adult cattle. In some instances, the diseases are referred to as calf diarrhea, calf scours or calf enteritis, and winter dysentery in adult cattle. Coronavirus effects calves as soon as their second week of life but can effect older calves as well. Heretofore, virus vaccines have been prepared by extensive passaging of the virulent virus. These known vaccines have proven to be clinically ineffective against many wild-type BCV infections. Coronavirus causes one of the most severe viral diseases of neonatal calves and may completely destroy the villi of the intestine. Evidence also suggests that some forms of Coronavirus contribute to respiratory disease. Coronavirus causes severe disease alone, but is influenced by coinfections with other enteropathogens. That is, concurrent infection with E. coli and/or rotavirus often complicates the disease process. Unlike bovine rotavirus, only one serotype of bovine coronavirus is known.
Rotaviruses (RV) cause acute gastroenteritis, malabsorptive diarrhea, and dehydration in severe cases. The disease severity is influenced by coinfections with other enteropathogens. Rotavirus is recognized as a distinct entity and is divided into six groups based upon how the proteins on its outer surface behave antigenically. Two of those groups—Group A and Group B—commonly infect cattle; within those groups, a number of different serotypes have been identified. The most common G serotypes of group A rotaviruses affecting calves are G6 and G10. G8 may also be emerging as a prevalent genotype. Three P serotypes have been identified in calves with scours: P6(1), P7(5) and P8(11).
The two non-viral pathogens addressed by this invention include Escherichia coli (E. coli) and Clostridium perfringens Type C (Cl. perfringens). E. coli pathogens are commonly found in the gut and the manure of healthy cattle, resulting in most calves being exposed shortly after birth. These bacteria attach to the lining cells of the intestine by means of hair-like projections called pili. These attached bacteria produce toxins that cause the intestine to secrete large amounts of fluid, which can result in scours, dehydration and death.
E. coli is divided into antigenic types based on adhesiveness factors on the surface of the cell wall and its ability to produce various toxins. Specific pilus formation appear to be controlled by DNA outside the chromosome. This DNA replicates autonomously and can thus be transferred from one E. coli to the next, often resulting in increased virulence and mutations in the field.
Cl. perfringens Type C commonly inhabits soil as well as the intestinal tracts of healthy cattle, meaning calves are easily exposed and infected. Changes in the environment of the calf's stomach allow the Type C organisms to grow, producing enterotoxins that cause severe symptoms and high death losses.
The vaccines of the present invention, accordingly, are prepared from virus and/or bacteria originally obtained in the field, and more specifically, are prepared from various combinations of bovine coronavirus, bovine rotavirus, E. coli and Cl. perfringens Type C originally obtained in the field. That is, they were obtained by collecting biological samples and identifying/isolating the specific strains.
Vaccines must contain the correct serotypes of the organisms responsible for scours in order to prevent it. Although available scour vaccines are carefully produced to insure they contain the organisms claimed on the label, there are differences in the number of serotypes in the products that are available. The best vaccine is one that demonstrates immunity in calves challenged with specific serotypes of the important scours-causing organisms.
Accordingly, there is a real and unsatisfied need in the art for new treatment modalities for cattle at risk for scours-causing infections, both in terms of a more effective and broader coverage vaccines. The novel scours vaccines disclosed herein comprise viruses that are propagated on cell cultures and an effective vaccine is prepared by inactivating the virus after it has been grown on other cell cultures. Therefore, this invention consists of polyvalent vaccines effective against neonatal calf scours comprising one or more inactivated viruses, may further comprise one or more bacterial strains, and methods of preparing and administering these vaccines.